Process for the continuous production of boron nitride

Claim 1

A PROCESS FOR THE PRODUCTION OF BORON NITRIDE, WHICH PROCESS COMPRISES THE STEPS OF: (1) INTRODUCING PARTICLES HAVING A THICKNESS UP TO 1-20 MM., SAID PARTICLES COMPRISING A SUBSTANTIALLY HOMOGENEOUS INTIMATE MIXTURE OF AN OXYGEN-CONTAINING BORON COMPOUND SELECTED FROM THE GROUP CONSISTING OF B2O3, H3BO3, ALKALI METAL BORATES, AND ALKALINE EARTH METAL BORATES, AND A SOLID, INERT, DILUENT MELTING ABOVE ABOUT 1300*C., HAVING A HIGH VOLUME TO WEIGHT RATIO OF ABOVE ABOUT 0.2 G./ML., AND CAPABLE OF BEING SEPARATED FROM BORON NITRIDE BY WASHING TECHNIQUES, SAID BORON COMPOUND, EXPRESSED AS B2O3, AND DILUENT BEING PRESENT IN A WEIGHT RATIO OF 1:2 TO 1:1 RESPECTIVELY, TO A PARTIAL NITRIDING ZONE IN CONTACT WITH AMMONIA FOR 10-80 MINUTES AT 500900*C., THE WEIGHT RATIO OF NH3 TO B2O3 BEING ABOUT 1:1 TO 3:1; AND (2) INTRODUCING THE RESULTANNT PARTICLES FROM STEP (1) INTO A FINAL NITRIDING ZONE IN CONTACT WITH AMMONIA AT ABOVE 900*C. FOR A PERIOD OF TIME APPROXIMATELY 60-100% OF THE CONTACT TIME EMPLOYED IN STEP (1), THE WEIGHT RATIO OF NH3 TO B2O3 BEING ABOUT 8:1 TO 12:1.